Serious health risks confront individuals working in a space subject to contamination with hazardous materials. A particularly dangerous space is one in which asbestos coatings are removed from surfaces inside a building. When these coatings are removed, fibers are released into the air and it is well established that these fibers pose a significant health risk. The coatings may be wetted down before removal to minimize the amount of fiber released into the air. However, enough fibers are still released to pose significant health risks.
It is known in the art to enclose an asbestos removal area to contain the released fibers. These enclosures may be formed of plastic sheets with as few seams as possible in order to prevent airborne asbestos fibers from spreading to other areas of the building. However, the air within the enclosures must eventually be exhausted and particulate matter in the exhausted air may become a health risk for persons in the building or, if it is exhausted outdoors, for those outside the building.
Thus it is known to provide free standing air filtration devices within the enclosure to remove particulate matter. For example, the air filtration devices may be arranged to blow air in a circular pattern around the inside of the enclosure. It is also known to direct the output of the air filtration devices directly on the workers within the enclosure to surround them with filtered air. However, this arrangement results in some areas of the enclosure being provided with higher air flow than other areas and allows particulate matter to collect in certain areas. Additionally, decontamination rooms, coupled to the work space, are commonly used. These rooms provide areas for the workers to store equipment, shower and change their clothing. Air flow is normally provided through the decontamination rooms to control the spread of particulate matter from the work space. Nevertheless, it has been determined that the particulate matter collects in the corners on the floors of these rooms.
U.S. Pat. No. 4,604,111 issued to Natale shows an enclosure around a source of hazardous particulate matter along with a decontamination chamber space. Air flow is provided through the enclosure and through the decontamination chamber. This air is then filtered and exhausted. However, the air inlet and outlet of the decontamination chamber are positioned such that an uneven or non-uniform pattern of air flow through the decontamination chamber and through the decontaminated areas may result before the air is exhausted. Thus the system of Natale still permits particulate matter to build up in the corners and thereby to form a health hazard.
When hazardous materials are removed in an occupied area, the concentration of particles around the enclosure is monitored at all times. It has been shown that in the systems of the prior art there are peaks of concentration at different points around the enclosure during removal of the toxic particulate. These peaks may exceed safe levels.